Much bigger chick

[4 chicks]

I have 4 chicks. 2 are barred rock and 2 are buff orpington. They are 2 1/2 weeks old. They range in size dramatically! One more so than the others. Its a barred rock and it is soo much bigger than the others. Legs are thicker, more feathers than the others more anti social than the others..lol What are my options? Is it a roo? Is it just older than the others? (even though when I first got them it didnt stand out to be any bigger than the others) Some one also said that maybe its just eating more than the others.
They are straight run...we are hoping for hens so I hope shes not a roo!! Here is a picture so maybe you can tell how much bigger she is.

 

[ChicKat]

It is bigger......

I would guess rooster, and maybe for the other barred rock too. It will be interesting to hear from BYC experts. I'm curious about what exactly is the reason......

 

[Sweetlilbaby]

My chicks are just days old. I hatched myself. They each are growing at different rates, and feathering at different rates. I wouldn't read much into the size difference and feathering difference yet. Wait til they all get bigger/older then see. It may be a rooster or it may just have hit a growth spurt before the rest did.